There has been an aircraft, a Drone actually, flying over the Yuma AZ Test Range, off and on for the last few months. It's a Solar-Electric powered drone that hit a new record altitude for a drone at 76,000 feet a few days ago. I was keeping tabs on it about a month or so ago, and it seemed to be aloft for 5 or 6 days. I would check it a couple of times a day and it was always aloft. Check out This Link It's flying right now.